1. Field of the Invention
The present invention relates to a charged beam drawing apparatus for drawing an LSI pattern by use of a charged beam.
2. Description of the Related Art
In an electron beam drawing apparatus, various kinds of electrostatic deflectors are used, such as a blanking deflector, a shaping deflector and an objective deflector. The electrostatic deflector has a plurality of deflecting electrodes, and gives a potential generated by a deflection amplifier to each of the electrodes, thereby deflecting an electron beam by an electric field generated between the electrodes.
One end of a coaxial cable is connected to an output end of the deflection amplifier, and the other end of the coaxial cable is connected to the deflecting electrodes of the electrostatic deflector. In general, since the deflecting electrodes of the electrostatic deflector are electrically connected to the coaxial cable alone, it is possible to consider that a capacity load is added to the end of the coaxial cable in terms of an equivalent circuit. Thus, a signal input from the deflection amplifier is substantially totally reflected by the deflecting electrodes, and the input signal returns to the deflection amplifier with a delay of a given time corresponding to the length of the coaxial cable. In such a state, high-speed operation of the deflection amplifier is difficult.
On the other hand, if the deflecting electrodes are connected to a ground via a resistance equivalent to a characteristic impedance of the coaxial cable, the reflection of the signal by the deflecting electrodes is suppressed, such that a high-speed operation can be performed (JP-A 11-150055(KOKAI)). However, in this case, since there is a current running to the resistance even if a voltage is in a constant state, a load on the deflection amplifier is increased. Therefore, it is difficult to raise a driving voltage. For example, given that 50Ω is used in a terminating resistance and that a voltage of 50V is applied thereto, a current of 1 A steadily flows at the maximum in the terminating resistance. This is not realistic because loads on the amplifier, the cable and the terminating resistance are heavy.
Thus, in the conventional electron beam drawing apparatus, it has been difficult to achieve high-speed high-voltage operation of the electrostatic deflector without increasing the load on the deflection amplifier. Moreover, the problem described above is true with not only the electron beam drawing apparatus but also an ion beam drawing apparatus.